Traditionally, most commercially available inkjet printers have a print engine which forms part of the overall structure and design of the printer. In this regard, the body of the printer unit is typically constructed to accommodate the printhead and associated media delivery mechanisms, and these features are integral with the printer unit.
This is especially the case with inkjet printers that employ a printhead that traverses back and forth across the media as the media is progressed through the printer unit in small iterations. In such cases the reciprocating printhead is typically mounted to the body of the printer unit such that it can traverse the width of the printer unit between a media input roller and a media output roller, with the media input and output rollers forming part of the structure of the printer unit. With such a printer unit it may be possible to remove the printhead for replacement, however the other parts of the print engine, such as the media transport rollers, control circuitry and maintenance stations, are typically fixed within the printer unit and replacement of these parts is not possible without replacement of the entire printer unit.
As well as being rather fixed in their design construction, printer units employing reciprocating type printheads are relatively slow, particularly when performing print jobs of full colour and/or photo quality. This is due to the fact that the printhead must continually traverse the stationary media to deposit the ink on the surface of the media and it may take a number of swathes of the printhead to deposit one line of the image.
Recently, it has been possible to provide a printhead that extends the entire width of the print media so that the printhead can remain stationary as the media is transported past the printhead. Such systems greatly increase the speed at which printing can occur as the printhead no longer needs to perform a number of swathes to deposit a line of an image, but rather the printhead can deposit the ink on the media as it moves past at high speeds. Such printheads have made it possible to perform full colour 1600 dpi printing at speeds in the vicinity of 60 pages per minute, speeds previously unattainable with conventional inkjet printers.
High print speeds require high precision and high speed paper movement, and as such, the entire print engine (printhead, paper handling mechanisms and control circuitry etc) must be configured accordingly to ensure high quality output.
Accordingly, there is a need to provide a print engine having a pagewidth printhead that can be readily employed within a printer body for consistent, high speed printing.
Unfortunately, individual nozzles on a printhead will malfunction through clogging, air bubbles in the ink, fabrication errors and so on. Obviously, this is detrimental to print quality. It is possible to combat this with dead nozzle compensation in the print engine controller (PEC) and nozzle redundancy (extra nozzles) on the printhead. However, eventually too many nozzles will fail for these mechanisms to work, and the print quality is compromised. By providing the printhead in a replaceable printhead cartridge, the printhead can be replaced when the print quality deteriorates, rather than replacing the entire printer.
A pagewidth printhead needs to be precisely mounted relative to the paper path. To do this with a replaceable printhead cartridge would typically require a fairly involved cartridge replacement procedure and or a complex cartridge cradle in the printer. This has disadvantages for both the end user and the manufacturer.